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Published September 20, 2017 | Supplemental Material
Journal Article Open

Operando Spectroscopic Analysis of CoP Films Electrocatalyzing the Hydrogen-Evolution Reaction

Abstract

Transition metal phosphides exhibit high catalytic activity towards the electrochemical hydrogen-evolution reaction (HER) and resist chemical corrosion in acidic solutions. For example, an electrodeposited CoP catalyst exhibited an overpotential, η, of -η < 100 mV at a current density of -10 mA cm^(-2) in 0.500 M H_2SO_4(aq). To obtain a chemical description of the material as-prepared and also while effecting the HER in acidic media, such electrocatalyst films were investigated using Raman spectroscopy and X-ray absorption spectroscopy both ex-situ as well as under in-situ and operando conditions in 0.500 M H_2SO_4(aq). Ex-situ analysis using the tandem spectroscopies indicated the presence of multiple ordered and disordered phases that contained both near-zero valent and oxidized Co species, in addition to reduced and oxygenated P species. Operando analysis indicated that the active electrocatalyst was primarily amorphous and predominantly consisted of near-zero-valent Co as well as reduced P.

Additional Information

© 2017 American Chemical Society. Received: July 20, 2017; Published: August 28, 2017. This work was based on work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the U.S. Department of Energy Office of Science under Award Number DE-SC0004993. Synchrotron measurements were performed at beamlines 7-3 and 14-3 at the Stanford Synchrotron Radiation Lightsource at SLAC National Accelerator Laboratory, which is operated by Stanford University for the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-76SF00515, and supported by the Office of Biological and Environmental Research, and by the NIH including P41GM103393. A.I.C. acknowledges a Graduate Research Fellowship from the National Science Foundation. The authors gratefully acknowledge R. Jones and Dr. K. Walczak for assistance with spectroelectrochemical cell fabrication. The authors declare no competing financial interests.

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